The present invention relates to a pressure reduction means installed in the brake circuit of the rear axle of a motor vehicle, comprising a master cylinder and at least one monitoring device, and this means executing the brake-pressure reduction only in specific circumstances.
A brake system employing such a pressure reduction means is disclosed particularly in German Patent Application DE-A-3,742,173.
According to this document, a branch line which can be opened or closed by means of a solenoid valve short-circuits the brake-pressure reduction means. This braking system has a serious disadvantage in that, in the event of a failure of the anti-lock function, the valve shutter of the solenoid valve, which must then rest on its seat so as to close this branch line, is subject to a high difference of pressures exerted on its opposite faces. This results in the need to use a spring for returning this shutter to rest, having a high prestress which the force generated by the solenoid of the solenoid valve has to overcome during normal operation. Thus, the solenoid valve is of a costly type since it has to be oversized to ensure that the braking system described is reliable.